SOARING FREE from gravity's grasp has always held an irresistible attraction for human beings. Mythology and science fiction are replete with tales of the fabrication of craft to carry people out of the earth's reach and into the firmament. But in none of these stories does a Daedalus or Buck Rogers ponder the possibility that gravity might be essential to the body's survival.

Since the first manned orbital flights in 1961, medical investigators have had the opportunity to monitor at least some of the vital functions of more than 200 men and women in microgravity surroundings. While study conditions have been less than ideal and subject populations small, they have been able to draw one conclusion. They have found that, for the most part, when the human spirit is willing to accept the conditions of weightlessness, the flesh is able.